1. Field of the Invention
The present invention relates to an electrolytic apparatus, and more particularly, it relates to an electrolytic apparatus employing subsidiary energy beams such as laser beams.
2. Description of the Prior Art
Examples of such conventional electrolytic apparatus can be seen in Japanese Patent Laying-Open Gazette No. 38235/1979 and U.S. Pat. No. 4,217,183. FIG. 1 shows an electrolytic apparatus disclosed in the above U.S. patent. Referring to FIG. 1, a metal layer 1 evaporated on an insulated substrate 2 forms a cathode. The cathode 1 is immersed with an anode 5 in an electrolyte 3 prepared as a plating solution of, e.g., cupric sulfate (CuSO.sub.4) contained in a vessel 4. A voltage modulator 7 is adapted to modulate voltage supplied between the cathode 1 and the anode 5 by a voltage source 6. The beam emitted from a beam generator 8 (laser source in this case) is modulated by the beam modulator 9 to be focused on the surface of the cathode 1 by a lens 11. The beam 10 is so manipulated by a scanning mirror 12 that a predetermined portion of the cathode 1 is exposed.
FIG. 2A shows the beam pulse waveform modulated by the beam modulator 9. FIG. 2B shows the voltage pulse waveform modulated by the voltage modulator 7 corresponding to the beam pulses shown in FIG. 2A, which is shown by the potential of the cathode 1 with respect to the anode 5.
Operation of the apparatus shown in FIG. 1 is now described. First, as shown in FIG. 2B, prescribed negative voltage pulses are applied to the cathode 1. In this case, the value of the electrolytic current is by far smaller than that for plating the whole surface of the metal layer 1. In such a condition, laser pulses whose periods are synchronized by the beam modulator 9 with those of the voltage pulses shown in FIG. 2B are applied to a predetermined position on the surface of the cathode 1 through the lens 11 and the scanning mirror 12. In this case, the laser beam is selected from the lasers of argon (Ar), krypton (Kr) and YAG etc. to have wavelength which can be transmitted through the electrolyte 3. The portion exposed by the laser beam 10 is electrochemically activated to be selectively and preferentially plated.
FIG. 3 shows portions 13 and 14 of a plated layer on the cathode 1 as plated in the aforementioned manner in a sectional view. The plated layer portion 13 corresponds to the region exposed by the laser beam 10, in which plating is selectively and preferentially facilitated. However, when the voltage pulses are applied, the region 14 not exposed by the laser beam 10 is also slightly plated. In electrolytic plating, further, when the ionization tendency of the metal layer 1 is stronger than that of metal ion in the electrolyte 3 as in the case silver (Ag) is plated on a cathode of copper (Cu) or nickel (Ni) etc., displacement plating is caused on the whole surface of the metal layer 1 by simply immersing the same in the electrolyte 3. As the result, the thinner plated layer 14 is formed on the region not exposed by the laser beam. When the plated layer 13 formed in the part irradiated by the laser beam is employed as a lead wire for an electric circuit or the same is applied only to a necessary region for saving material in noble metal plating, the plated layer 14 in the unirradiated part is unnecessary or even obstructive. Therefore, the plated layer in the said region 14 must be removed by a proper method such as pickling.
As hereinabove described, in the conventional electrolytic plating apparatus, the thinner plated layer is inevitably formed in the undesired region and hence it is required to remove the unnecessary plated layer, whereby the steps in the plating process are increased. Further, insufficient removal of the unnecessary plated layer will result in inferior goods.